docs: def triangulate(self):
          """
          Convert mesh points to vectors in Cartesian space.
  
          :returns:
              Tuple of four elements, each being 2d numpy array of 3d vectors
              (the same structure and shape as the mesh itself). Those arrays
              are:
  
              #. points vectors,
              #. vectors directed from each point (excluding the last column)
                 to the next one in a same row →,
              #. vectors directed from each point (excluding the first row)
                 to the previous one in a same column ↑,
              #. vectors pointing from a bottom left point of each mesh cell
                 to top right one ↗.
  
              So the last three arrays of vectors allow to construct triangles
              covering the whole mesh.
          """
          points = geo_utils.spherical_to_cartesian(self.lons, self.lats,
                                                    self.depths)
          # triangulate the mesh by defining vectors of triangles edges:
          # →
          along_azimuth = points[:, 1:] - points[:, :-1]
          # ↑
          updip = points[:-1] - points[1:]
          # ↗
          diag = points[:-1, 1:] - points[1:, :-1]
  
          return points, along_azimuth, updip, diag